A carding machine generally has a rotatable drum whose outer surface is provided with a card clothing in turn having a dense array of teeth or little hooks. The machine also has several covers provided with linings directed radially inward at the drum and also provided with similar card clothings. The covers are arranged about a portion of the periphery of the drum so that the outer card clothings on the covers of the housing interact with the inner card clothings on the drum outer surface.
When the carding machine is in use fibers are drawn from a region of the drum where there is no cover. The fibers are passed over the little hooks on the cover of the carding machine. As this happens the card clothings mounted on the covers engage into the fibrous material so that together the drum and the cover act on the fibers to work the fiber material and orient the fibers. To this end the covers can be moved along a portion of the periphery of the drum against the rotation direction of the drum. Since only the relative speed is important for the interaction of the drum and the cover. It is also possible to use a fixed-cover system where only the drum moves and the covers are fixed in position.
In order to uniformly orient the fibers it is extremely important in both systems that the little hooks or teeth of the card clothings have a uniform height. Card clothings of the above-described type with a sufficiently uniform height of the teeth or hooks are described in Swiss patent 644,900, Swiss patent 655,521, Swiss patent 659,832, and British 2,236,543. With the card clothings described in these publications the cover linings are formed as a plurality of parallel sawtooth-wire strips and the support structure extends as a single piece under the entire foot region of these sawtooth-wire strips.
Since the card clothings are subjected to a great deal of wear during use of the carding machine and thus have to be changed often, such a construction is disadvantageous with respect to the considerable amount of material needed for the support structure.
In order to overcome this disadvantage Swiss patent 654,341 proposes to solder or weld together individual sawtooth-wire strips at their foot regions and to mount the thus formed sawtooth-wire strip pack without use of a support structure directly on the covers of a carding machine.
The construction of such sawtooth-wire strip packs with an adequate uniformity of tooth height is very expensive to produce because it requires a number of very precisely executed welding operations. For this reason the use of card coverings such as described in Swiss patent 654,341 is very disadvantageous from a practical point of view.
According to a suggestion described in above-named Swiss 655,521 the sawtooth-wire strips forming the cover linings are each provided in their foot region with a recess and a card clothing is formed therefrom with a bar-like support guide extending through these recesses. Then the sawtooth-wire strips are held in position on the bar with the aid of latching parts. With such a construction producing the recesses in the foot region of the individual sawtooth-wire strips must be done with extreme precision in order to ensure a uniform tooth height of the finished card clothing. In addition the bar-like support must be fitted with great precision in the recesses in order to prevent a shifting of the sawtooth-wire strips on the support. For this reason the manufacture of card coverings according to this proposal entails very high production costs.